From http://en.wikipedia.org/wiki/Drum kit;                A drum kit (also drum set or trap set) is a collection of drums, cymbals and sometimes other percussion instruments, . . . arranged for convenient playing by a single drummer . . . The exact collection of drum kit components depends on factors like musical style, personal preference, financial resources, and transportation options of the drummer. Cymbal, hi-hat, and tom-tom stands, as well as bass drum pedals and drummer thrones are usually standard. Most mass produced drum kits are sold in one of two 5 piece configurations (referring to the number of drums only) which typically include a bass drum, a snare drum, and three toms. The standard sizes (sometimes called ‘rock’ sizes) are 22″ (head size diameter) bass drum, 14″ snare drum, 12″ and 13″ mounted toms, and a 16″ floor tom. The other popular configuration is called Fusion size, a reference to Jazz fusion music, which usually includes a 22″ bass drum, a 14″ snare drum, and 10″, 12″ and 14″ mounted toms. The standard hardware pack includes a hi hat stand, a snare drum stand, two or three cymbal stands, and a bass drum pedal. Drum kits are usually offered as either complete kits which include drums and hardware, or as “shell packs” which include only the drums and perhaps some tom mounting hardware. Cymbals are usually purchased separately and are also available in either packs or as individual pieces.An illustration of a typical drum kit is shown in FIG. 24. The kit consists of Bass drum 201, Floor tom 202, Snare 203, toms 204, Hi-hat 205, and Crash and Ride cymbals 206. Floor toms tend to be larger in diameter and longer in length and thus heavier than suspended toms.        
Drum mounting is usually done in one of three arrangements. Rack or stand mounted drums typically use a stand that has an upright metal pole or tube attached to a three-legged base, herein referred to as a “tripod stand”. This stand usually has two small arms at the top that permit the stand to hold one or two tom drums by various means, using holders that fasten to the drum. These mounts or holders attach to the shell of the drum or, if suspended, attach to a suspension bracket.
Common prior art suspension brackets were die cast or metal and directly affixed to the shell of a drum. Such rigidly connected systems inhibited the ability of the shell to resonate fully with the vibrating drum head, and resulted in adverse acoustical effects.
Most modern drums have wooden shells which may vary in thickness from one-eighth to one-half of an inch. This variation in shell thickness can cause a considerable variation in the weight of the drums, even though they may have identical diameters and heights. For example, a thirteen-inch diameter by nine-inch tall drum with a three-sixteenths-inch thick shell may weigh approximately eight pounds, while a thirteen-inch diameter by nine-inch tall drum with a one-half-inch thick shell may weigh approximately twelve pounds. Some shells are made of plastic or fiberglass, which have even greater weight. And some shells are made of composites such as carbon fiber which results in a very light shell.
Drums are typically manufactured in standard diameters of eight, ten, twelve, thirteen, fourteen, fifteen, sixteen, and eighteen inches. Drum heights vary significantly, but when intended for rack-mounting, the heights are typically less than the diameters. Drums having a height as long or longer than the diameter, such as fourteen-by-fourteen, sixteen-by-sixteen, or eighteen-by-eighteen, are typically set on the floor since they are too heavy to be practical for rack mounting (See item 22 of FIG. 24 as an example).
Another alternative (not shown) uses a three-legged base attached to an upright pole that has three arms that extend from the top. A mechanical means such as a screw projects up through the center of the three arms and is designed to adjust the arms in or out by rotating the screw through the handle or knob attached to the end of the screw. This action creates a ‘clamping’ force to the bottom hoop of the drum. The arms are usually spaced equally apart at about one-hundred and twenty angular degrees.
Some prior art drum mounting systems, such as those demonstrated in the present inventor's U.S. Pat. No. 4,158,980, included an arcuate frame structure that was slightly larger than the radius of the drum, and extended one hundred and eighty angular degrees or more around the drum shell. Such mounting systems eliminated the commonly employed bracket from the shell and instead incorporated a support that was affixed to the frame encircling the drum. The arcuate frame was attached to the drum's tuning rods using vibration dampening grommets. Such systems attempted to prevent the resonance of the drum from being choked or dampened by the mounting system, thereby attempting to prevent the aforementioned adverse acoustical effects.
Such a system as those demonstrated in U.S. Pat. No. 4,158,980 typically employed three or more metal L-shaped brackets extended from the frame and attached to the tuning rods. This change demonstrated a dramatic and very noticeable improvement over the common mounting systems precedent thereto in tonal quality, frequency range and overall resonance of the instrument, since the shell was now able to act unrestricted and in concert with the vibrating drum head. This structure worked very well as long as the drum was positioned perpendicular to the ground or with the drum head being parallel to the floor. The weight loading of the drum in this position placed the center of gravity in the center of the drum therefore dividing the weight of the instrument evenly among the L-shaped brackets in the contact areas around the drum's radius.
However, such systems as those demonstrated in U.S. Pat. No. 4,158,980 were deficient when the drum was angled or tilted into a common playing position as required by most players of the instrument. This changes the center of gravity, thereby shifting the weight loading on the L-shaped brackets unevenly about the drum. Depending on the amount of angle, the increase or decrease in the shifting weight at these points can be substantial and change the pressure against the shell. When the drum was level or in plane with the floor the weight was evenly distributed with the load being directed straight down or perpendicular to the floor at all attachment points, but as the drum was tilted, greater pressures against the shell created a damping effect by preventing the shell from vibrating.
To hold or suspend a drum or any vibrating object without interfering with its resonance is a function of balance. When a drum vibrates along with the head, it becomes a vibrating entity. Every part of the drum wants to vibrate freely. If the drum or any part of it is restricted by pressure against any part of its structure, it will affect the resonance and therefore part of its frequency response. This change can occur from even slight pressure or change in pressure to any part of the drum. This characteristic along with the variations from one drum to another can produce an infinite number of results when it comes to problems and solutions in drum vibration.
The more extreme the angle of drum tilt, the greater the pressure against the shell, and the more damping would occur in such systems, especially at the lower part of the angled drum. The upper side of the tilted drum would then realize less weight, creating less pressure against the shell. As the angle of the drum was increased, the function or ability of the rubber grommets to isolate resonance would be diminished and the grommets would change more to absorbing resonance, which is determined by the weight load shift occurring at the points of contact. The rubber isolation grommets would now be dampening resonance in the contact areas of greater weight due to the shifting balance. In fact, as an admission of this, U.S. Pat. No. 4,158,980 refers to the grommets as “vibration absorbing means”. The tilted drum would now begin to show a noticeable decrease in tonal quality and resonance due to the change in the drum's center of gravity.
When commercialized, such rubber grommets were typically made from mixing rubber compounds to soften or harden the material, altering its durometer or hardness. By mixing rubber compounds to create different durometers, it was possible to isolate specific frequencies. In practice, the grommets were typically made of a mid-range durometer, since most drums can be tuned to a wide range of frequencies. Providing the drummer with a variety of grommets to change according to the tuning of the drum and thereby isolate the tuned frequencies was not practical, for many obvious reasons, and would not be effective even if practical, since shifting of the center of gravity whenever the drum's tilt angle was changed would alter the grommet's ability to function properly anyway.
A drum head typically contains three basic components; a head skin (usually made of polyethylene-terephthalate or an equivalent material in modern drums), a hoop (usually made of aluminum), and some type of glue or adhesive (usually epoxy resin) to attach or fasten the skin in or to the hoop. This type of head is the most common and is known as a chemically-bonded head because of the glue or chemicals used in its fabrication. Another type of head uses only two basic components in its structure. This is a called mechanical head because the skin is crimped or clamped inside the aluminum hoop and thereby affixed thereto by mechanical means. Either of these types of heads may be employed within the present invention.
When the drum head is placed on the top or bottom of the drum shell it becomes contoured over the bearing upper edge of the shell and the hoop extends around and beyond the edge, leaving a very slight gap or overhang between the outside of the shell and the drum head hoop. This is important, because only the head's skin should be touching the bearing edge of the shell. This bearing edge is similar to the bridge on a string bass or violin. It creates a stopping point for the drum head from where its vibration begins (or ends). It also creates a firm surface that allows the resonance of the vibrating head to transfer to the drum shell.
The hoop part of the drum head is actually isolated from the vibration of the head by the bearing edge contact. A counter hoop, usually die cast of aluminum or stamped from steel, is placed over the drum head to create a means for changing the tension or pitch of the drum head. Threaded tension rods are used around the counter hoop to pull the head skin and hoop down over the bearing edge, thus tightening the skin across the top or bottom of the drum. The tension rods additionally allow tuning of the drum by increasing tension on the head skin when tightened and reducing such tension when loosen. A tighter head skin will have higher resonant frequencies than an otherwise equivalent but looser head skin.
Another drawback of the mounting system demonstrated in U.S. Pat. No. 4,158,980 is that the attachment points of the mounting frame are located at four or more tension rods. Resonance that comes from the vibrating shell after the drum head is struck transfers through the metal castings that attach to the shell surrounding the drum, creating additional adverse acoustical effects.